I guess the point that I would make is that if you have something that is 47 metres away, you should have no interest left in the chart - only in whatever is 47 metres away!

"Something" is not 47 meters away. It is a nautical mile away - with an uncertainty of 47 meters. And that may be for each LOB of the three used to make the fix.

I thought the reasoning that brought us this far down the thread was: Don't trust GPS in a coastal waters - use coastal piloting techniques. [#20]

I will cease and desist now, but reiterate one last time that GPS, with or without WAAS, is more accurate than coastal piloting can be. (for all the reasons stated above) No one said anything about not looking out the port holes! If GPS fails, then coastal piloting is a perfectly reasonable alternative, and always a useful check of a working GPS fix.